The 36-year-old man was heard screaming for help as the collapse occurred around 11 p.m. on Thursday night.

"When [his brother] got there, there was no bedroom left," Hillsborough County Fire Rescue spokeswoman Jessica Damico told The Associated Press. "There was no furniture. All he saw was a piece of the mattress sticking up."

An arriving police officer pulled the brother from the still-collapsing house. There's been no contact with the man since then and adjacent neighbors have been evacuated.

"We put engineering equipment into the sinkhole and didn't see anything compatible with life," Damico said.

Rescuers cannot continue until engineers determine the borders of the naturally-occurring hole, which is estimated to be about 30 feet across above the surface — as many as 100 feet wide underneath — and about 20 feet deep.

"The entire house is on the sinkhole," Damico said. Five adults and one 2-year-old child were inside the home when chasm opened up.

CNN notes that the ground coveringthe massive cavity could buckle, taking the entire house as well as neighboring homes down with it.

Sinkholes are common in Florida because the state lies on bedrock made of limestone or other carbonate rock that can be eaten away by acidic groundwater, according to the Florida Department of Environmental Protection.